Method and apparatus for identifying a signal route for delivery of video-on-demand to a subscriber terminal

ABSTRACT

A set top box includes an interface to a video system configured to deliver data to an individual subscriber or subset of subscribers that are part of a larger group of subscribers, wherein the data is not delivered to the other subscribers of the larger group, the interface adapted to receive communications from one or more modulators of a modulator group of the video system. The set top further includes a decoder configured to extract a modulator group identifier periodically inserted into communications directed to the set top box from the one or more modulators, the modulator group identifier unique to a physical transmission path from a headend of the video system to the one or more modulators. The set top includes a video request interface to the video system, the video request interface configured to output a request for video data including the modulator group identifier.

RELATED APPLICATIONS

This application claims priority under 35 USC 119 and 120 from U.S.Provisional Patent Application No. 60/176,393 filed Jan. 13, 2000 andentitled “Method and Apparatus for Identifying A Signal Route forDelivery of Video-On-Demand To A Subscriber Terminal”; U.S. patentapplication Ser. No. 09/759,935 filed on Jan. 12, 2001 and entitled“Method and Apparatus for Identifying A Signal Route for Delivery ofVideo-On-Demand To A Subscriber Terminal,” and issued on Apr. 9, 2013 asU.S. Pat. No. 8,418,214; and, U.S. patent application Ser. No.13/843,104 filed on Mar. 15, 2013, entitled “Identifying a Signal Routefor Delivery of Video-on-Demand to a Subscriber Terminal,” issuing onAug. 4, 2015 as U.S. Pat. No. 9,100,703; the full disclosures of each ofthe applications are hereby incorporated by reference in their entirety.

APPENDIX

The attached Appendix A (pages A1-A6) contains information about theISO/IEC JTC 1/SC 29 standard entitled “Coding of Audio, Picture,Multimedia and Hypermedia Information”.

BACKGROUND OF THE INVENTION

The invention relates to the field of delivery of video-on-demand (VOD).More particularly, the invention relates to identification of anaudio/video signal path from a video server to a subscriber terminal.

Typically, cable TV networks, such as CNN and video programming from aVOD server, transmit audio/video programming signals from a cable hub ora headend facility to one or more cable subscribers via a hybrid fiberoptic and coaxial cable (HFC) television network. In accordance withNational Television Standards Committee (NTSC), the video signals arecarried in 6 MHz channel slots that are kept separate by using frequencydivision multiplexing (FDM). Each separate baseband video signal isassigned a unique radio-frequency (RF) and up-converted to its assignedRF frequency so that multiple signals may simultaneously share the HFCnetwork in accordance with FDM.

Programming signals from the hub or headend are typically transmitted aseither analog signals or as digital transport streams. For example, eachanalog audio/video programming signal may occupy a 6 MHz channel. Anexample of a digital protocol by which the digital transport streams maybe communicated is Moving Pictures Experts Group (MPEG or MPEG-2) whichis described in more detail in the attached Appendix A. MPEG-2 is astandardized protocol by which moving pictures and accompanying soundtracks may be communicated digitally. This standard defines datapackets, each including a packet header and data field. For digitalnetworks or video server programs, multiple digital signals or programsmay share a 6 MHz channel. The digital signals are typically transmittedusing quadrature amplitude modulation (QAM). QAM-64 and QAM-256 aretypical QAM modulations schemes. Typically, a combination of analog andQAM signals may be transmitted to cable subscribers via the HFC networkusing FDM. A QAM-256 modulator has a throughput of approximately 38Mbps, which is equivalent to ten simultaneous audio/video programs, eachat 3.8 Mbps VOD.

Multiple HFC networks or paths from each hub carry cable programming todifferent areas, such as different geographic neighborhoods. For non-VODcable networks, an up-converter is typically used to broadcastprogramming signals over all of the HFC networks in a corresponding 6MHz slot or RF channel frequency. Additional up-converters may broadcastadditional signals to all of the HFC networks in other RF channels.Thus, each neighborhood receives all of the same programs over thecorresponding RF channel frequencies.

For VOD, however, such a scheme of broadcasting VOD programming to everyarea or neighborhood may be inefficient. For example, assume that a hubfeeds three HFC networks, where each HFC network provides data to adifferent neighborhood. Assume also, for example, that to meet demandfor VOD, each neighborhood requires a maximum of twenty simultaneousprograms. Assuming that one QAM channel is required for every tenprograms, twenty programs is equivalent to 2 QAM channels or 12 MHz. Forall three neighborhoods, the video server in the hub would need tosupport 60 simultaneous video programs so that 6 QAM channels would berequired. If all 6 QAM channels are up-converted and broadcast on allthree HFC networks, 36 MHz of bandwidth would be required on each HFCnetwork. However, because each neighborhood may be expected to requireonly 12 MHz of bandwidth, this technique has a disadvantage of resultingin unnecessary bandwidth being provided to each neighborhood.

Therefore, what is needed is a technique and system for delivery of VODdata which does not suffer from the aforementioned drawback of typicalsystems. It is to this end that the present invention is directed.

SUMMARY OF THE INVENTION

The invention is a method and apparatus for identifying an appropriatevideo signal path for delivery of video-on-demand (VOD) to a subscriberin a VOD system. In the VOD system, each signal path from a VOD serverservices only the subscribers within a designated area or neighborhood.The signal path may be a portion of a hybrid fiber optic and cable (HFC)network. The other unused signal paths in the HFC network may thenservice subscribers in other areas. Because each path need not serviceevery area, the total bandwidth provided by the VOD server need not beprovided to every area so that bandwidth is not wasted. Rather, thebandwidth provided to each area can be commensurate with the needs ofthat area.

In accordance with the invention, a unique identification may assignedto each area. The video server may periodically transmit the appropriateidentification to the subscriber terminals of each area. The subscriberterminals may be pre-configured to receive the unique identification.When a subscriber requests VOD programming, the identification receivedby the subscriber's terminal from the VOD server is returned to theserver along with the request. From the identification, the VOD servermay determine the area in which the requesting subscriber is located.The VOD server may then transmit the requested programming to the areain which the subscriber is located for reception by the subscriber. Thisprevents the VOD server from having to unnecessarily send the requestedprogramming to all the other areas.

In accordance with one aspect of the invention, a VOD server identifiesan appropriate video signal path for delivery of VOD to a subscriber ina VOD system. The subscribers may be arranged according to a pluralityof groups, each group having one or more corresponding signal paths fromthe server to the subscribers of the group. Each group receives acorresponding identification from the server. A subscriber request forprogramming from the server includes the identification associated withthe group to which the subscriber belongs. In response to the request,the server provides the requested programming to the subscriber via thesignal path which corresponds to the group.

Thus, in accordance with the invention, a video on demand headend fordistributing video on demand to one or more groups of subscribers isprovided wherein each group of subscribers is serviced by one or moremodulators connected to the headend wherein each modulator modulates thevideo on demand data at a different frequency. The headend comprises avideo server, an application server connected to the video server, meansfor periodically generating a unique identification packet for eachgroup of subscribers, means for receiving a request for video on demanddata from a subscriber, the request comprising the unique identificationpacket for the group of subscribers to which the subscriber belongs, therequest for particular video on demand data and a unique subscriberidentifier, and means for selecting a modulator from the one or moremodulators servicing the group of subscribers to which the subscriberbelongs based on the unique identification packet.

In accordance with another aspect of the invention, a video on demandsystem for distributing video on demand is provided, comprising aheadend having a video server and an application server and one or moremodulators connected to the headend, one or more groups of subscriberseach being serviced by one or more modulators, the one or moremodulators servicing a particular group of subscribers modulating thevideo on demand data at different frequencies so that the modulatedsignals to the particular group of subscribers share the same physicalmedia. The headend further comprises means for assigning a unique plantidentifier for each group of subscribers so that video on demand datadestined for a particular group of subscribers is modulated using theone or more modulators that service that particular group ofsubscribers.

In accordance with another aspect of the invention, a video on demanddelivery method for distributing video on demand to one or more groupsof subscribers wherein each group of subscribers is serviced by one ormore modulators connected to a headend, each group of subscribers beingassigned a unique plant identification is provided. The method comprisesreceiving the unique plant identification by a particular subscriber,generating a video on demand data request by the particular subscriberto the headend, the video on demand data request including the uniqueplant identification, the data request and a unique subscriberidentification, and selecting, at the headend, a modulator from the oneor more modulators assigned to the group of subscribers that theparticular subscriber is part of, based on the unique plantidentification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a video on demand (VOD) system in accordance withthe invention;

FIG. 1B illustrates the video path assignment in accordance with theinvention; and

FIG. 2 illustrates a method for identifying a VOD signal route inaccordance with the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The invention is particularly applicable to a QAM-based VOD system andit is in this context that the invention will be described. It will beappreciated, however, that the system and method in accordance with theinvention has greater utility.

FIGS. 1A-B illustrate a block schematic diagram illustrating an exampleof a preferred embodiment of a video-on-demand (VOD) system inaccordance with the present invention. A hub or headend 100 may includea video server 102 and an application server 104 which are connectedtogether. In a preferred embodiment, the video server 102 may be, forexample, an nCube Corporation MediaCube and may include one or morepieces of software or software modules being executed by the one or moreprocessors (not shown) of the video server such as an operating system(e.g., from nCube Corporation), a real-time streaming protocol (RTSP)application program (e.g., from nCube Corporation) and an video serverapplication program (e.g., from Oracle Corporation). The video server102 is well known and, thus, elements thereof may be altered or may besubstituted by others without departing from the invention. The videoserver 102 may also include a data formatter 106, which formats digitalaudio/video data into a form suitable for transmission. In a preferredembodiment, the data formatter 106 may include, for example, a wellknown MPEG multiplexer. In a preferred embodiment, the applicationserver 104 may include a Sun Microsystems Ultra-5 server running aSolaris operating system (also available from Sun Microsystems), adatabase application program (e.g., an Oracle-8 available from OracleCorporation) and other application programs (e.g., in Java language).The application server 104 may be conventional and, thus, elementsthereof may be altered or may be substituted by others.

Audio/video data, such as motion picture programming and the like, maybe generated by the video server 102 from prestored video programs ormovies stored in the video server's attached storage devices or may bestored remotely from the video server and communicated to the videoserver. The audio/video data may be formatted for transmission by thedata formatter 106. For example, the audio/video data may be formattedin accordance with MPEG-2 multiple program transport stream (MPTS)digital video signal standard for digital video broadcast, asynchronousserial interface (DVB/ASI). In a preferred embodiment, the formattedDVB/ASI video data may include, for example, up to sixty-twosimultaneously broadcast programs (“programs”). Selected programs maythen be provided to each of a plurality of well known quadratureamplitude modulation (QAM) modulators 108-118 (QAM 1-QAM 6 in theexample shown). For example, programs 1-2 may be reserved; programs 3-12may be provided to modulator 108; programs 13-22 may be provided tomodulator 110; programs 23-32 may be provided to modulator 112; programs33-42 may be provided to modulator 114; programs 43-52 may be providedto modulator 116; and programs 53-62 may be provided to modulator 118.Each modulator may include an up converter (U/C) 119 as is well known.In a preferred embodiment, the modulators 108, 112, 116 may up-convertthe video signals to a 300 MHz frequency for transmission while themodulators 110, 114, 118 may up-convert the video signals to a 306 MHzfrequency for transmission. It will be apparent that other transmissionfrequencies may be selected. In addition, the modulators 108-118 may beincorporated into the hub 100, for example, as part of the video server102.

Each group of programs may then be routed to one or more groups ofsubscribers 132-136 (See FIG. 1B) via one or more corresponding networklinks 120-130, such as in a hybrid fiber optic and coaxial cable (HFC)network. Because network links 120 and 122 may be frequency-divisionmultiplexed (FDM), the links 120 and 122 may share the same physicaltransmission media. Similarly, other links 124, 126 and 128,130 mayshare the same physical media. Each designated grouping of RFup-converted QAM modulators from which a given group of subscribers mayreceive a video signal may be referred to as a plant (e.g., Plant A,Plant B and Plant C is the example shown in FIG. 1A). Thus, modulators108 and 110 may correspond to Plant A which services subscriber group132; modulators 112 and 114 may correspond to Plant B which servicessubscriber group 134; and modulators 116 and 118 may correspond to PlantC which service subscriber group 136. Each plant may represent one ofthe physical HFC networks extending from a headend or hub through anoptical node to a neighborhood.

Each group of subscribers 132-136 may be located in a different area orneighborhood. Each subscriber terminal, e.g., terminal 138, in a plantor subscriber group may include well known audio/video reception anddisplay apparatus (not shown), such as, for example, a set-top box and atelevision set and may be located in subscriber homes or places ofbusiness.

In addition to transmitting audio/video data requested by subscribers,each plant may also transmit an identification designator to thesubscribers serviced by the plant. For this purpose, each plant may beassigned a unique plant identification code name or number. In theexample shown, Plant A may be assigned a first identification (Plant ID1) which is communicated to subscribers of group 132; Plant B may beassigned a second identification (Plant ID 2) which is communicated tosubscribers of group 134; and Plant C may be assigned a thirdidentification (Plant ID 3) which is communicated to subscribers ofgroup 136. In the preferred embodiment, the identifications arepacketized by the data formatter or MPEG-2 multiplexer 106 into packets(referred to herein as “identification packets”) in accordance with theMPEG-2 standard (described in more detail in the attached Appendix A) inwhich header information identifies the packet's program identification(PID) which correlates its payload type as “user data” in the programmap table (PMT) packet. The payload in this case includes theappropriate identification code or name. An appropriate identificationpacket is preferably transmitted recurrently (e.g., every 1 second) toeach of the subscriber groups 132-136 via one of the modulatorsassociated with each plant. For example, the identification packets maybe transmitted by the 300 MHz modulators 108, 112 and 114. In whichcase, the subscribers of each group may monitor the received 300 MHzsignal for the identification packets.

The subscriber terminals of the groups 132-136 may be pre-configured tomonitor the received signals for the plant identification packets by anappropriate application program which is pre-loaded into the subscriberterminals. For example, the application program may be loaded at thetime of manufacture or installation of each subscriber terminal.Alternately, the application program may be provided to the subscriberterminals by the application server 104, or by another applicationserver, over a LAN 146 and a well known quadrature phase shift key(QPSK) modem 144 via forward path 140 or via a broadcast file system(BFS), such as Scientific Atlanta Inc.'s network controller BFS.

Thus, the plant identification may be transmitted as an MPEG stream byat least one of the modulators 108-118 for each plant. For example, atleast one of the modulators 108-118 on each plant may carry the uniqueidentification as an MPEG program in its multiplex. The modulators foreach plant which contain the identification program may all have thesame RF up-converted frequency assignment (e.g., 300 MHz). Thesemodulators are referred to herein as the reference modulators (e.g.,modulators 108, 112, 116). The unique plant identification for eachplant may be defined while configuring the VOD system. Theidentifications may be inserted into an MPEG transport packet by awrapper program and stored by the video server 102 or accessible to it.The plant identification packets may be repeatedly transmitted alongwith other MPEG programming (typically video and associated audio) oralone via the RF channel associated with the reference modulator. Now, amethod for identifying a VOD signal route in accordance with theinvention will be described in more detail.

FIG. 2 illustrates a method 200 for identifying a signal route for aparticular piece of VOD data, such as a movie, to a particularsubscriber that belongs to a particular Plant. In more detail, when asubscriber, such as a subscriber at terminal 138, desires to order amovie, the subscriber may turn to the movie channel on their set-topbox. Then, a VOD application may be launched in their set-top box instep 202. This application program may be resident in the set-top box ormay be downloaded from the application server 104, or anotherapplication server, upon the subscriber accessing the subscriberchannel. The application program may cause the terminal 138 to tune tothe RF channel defined as the reference modulator (e.g., 300 MHz) instep 204. The terminal may then receive an identifier packet in step 206and then read the plant identification by extracting the MPEG user datawithin a pre-assigned MPEG program number in the MPEG multiplex on thatreference modulator (e.g., for the terminal 138, the reference modulatoris the modulator 108).

The set-top box of the subscriber terminal (e.g., the terminal 138) maythen communicate the plant identification, along with the movie request,to the application server 104 of the hub 100 in response to thesubscriber requesting a movie or other programming in step 208. Anidentification unique to the subscriber terminal may also be sent to thehub 100. For example, the subscriber terminal may communicate with thehub via a forward path 140 and a return path 142, the QPSK) modem 144and the local area network (LAN) 146. The forward and return paths 140,142 may be part of an HFC network. It will be apparent, however, thatcommunication between the subscriber terminals and the hub 100 may beprovided by another means, such as a LAN, a direct telephone connectionor the world-wide web (Internet).

Upon reception of the plant identification and subscriber terminalidentification, the application server 104 may determine whichmodulators, video server 102 output connector and program numbers servethat particular subscriber terminal. The hub 100, therefore, candetermine which of modulators 108-118 are capable of reaching therequesting subscriber. The requested video programming may then betransmitted by a modulator within the appropriate plant. For example,terminal 138 is serviced by Plant A. Therefore, modulators 108 and 110are both capable of reaching the subscriber terminal 138. However, asshown in FIGS. 1A-B, the modulators 112-118 are not capable of reachingthe subscriber terminal 138.

An available program may then be selected from the corresponding programnumbers (e.g., for plant A, one of programs 3-22 may be selected) fortransmitting the requested programming to the subscriber. The selectedQAM modulator RF frequency and program number may then be communicatedto the requesting subscriber terminal, such as the terminal 138, viaforward path 140. In response, the set-top box of the subscriberterminal, e.g., terminal 138, may then configure itself to receiveaudio/video data from that QAM modulator. The video server 102 may thenprovide the requested programming to the subscriber via the selectedchannel in step 210. Once the program is complete, the transmission maybe terminated. During transmission of programming to a subscriberterminal, other terminals in the groups 132-136 may interact with thehub 100 in this manner to receive requested programming. Thus, byassigning a subset of the modulators 108-118 to each of the subscribergroups 132-136, available bandwidth of the system is utilizedefficiently. The excess bandwidth may be used for other programming.

While the foregoing has been with reference to particular embodiments ofthe invention, it will be appreciated by those skilled in the art thatchanges in these embodiments may be made without departing from theprinciples and spirit of the invention, the scope of which is defined bythe appended claims. For example, the number of modulators and programsfor each plant may be altered. In addition, the number of plants may bealtered. Further, the specific protocols and modulation parametersdisclosed herein may be altered. The system may also include multipleDVB/ASI channels to multiple sets of QAM modulators, thereby alteringthe number of modulators shown in FIGS. 1A-B.

What is claimed is:
 1. A set top box, comprising: a video receiverinterface to a video-on-demand system, the video receiver interfaceadapted to receive communications from a modulator group of thevideo-on-demand system; a decoder configured to extract a modulatorgroup identifier periodically inserted into communications directed tothe set top box from one or more modulators of the modulator group, themodulator group identifier unique to a physical transmission path from aheadend of the video-on-demand system to the one or more modulators ofthe modulator group; and a video request interface to thevideo-on-demand system, the video request interface configured to outputa request for video-on-demand data including the modulator groupidentifier.
 2. The set top box of claim 1, further comprising: thedecoder configured to receive, via the video receiver interface, aprogram slot associated with the one or more modulators and assigned tovideo-on-demand data received in response to the request forvideo-on-demand data including the modulator group identifier, and anidentification of a modulator of the modulator group selected to deliverthe video-on-demand data; and the decoder configured to cause the settop box to tune to the program slot associated with the one or moremodulators and to the modulator of the modulator group selected todeliver the video-on-demand data.
 3. The set top box of claim 1, whereinthe decoder is configured to extract the modulator group identifier fromthe program streams directed to the set top box from the one or moremodulators.
 4. The set top box of claim 3, wherein the decoder isconfigured to extract the modulator group identifier from MPEG streamsdirected to the set top box from the one or more modulators of themodulator group.
 5. A computer implemented method to requestvideo-on-demand data, comprising: extracting, from a data streamreceived from a video distribution network, a periodically recurringmodulator group identifier for one or more modulators forming amodulator group that services a plurality of subscriber terminals, themodulator group identifier unique to a physical transmission path from aheadend to the one or more modulators; transmitting to the videodistribution network a request for video-on-demand data, the request forthe video-on-demand data including the modulator group identifier; andreceiving the video-on-demand data from an assigned modulator of thephysical transmission path associated with the modulator group.
 6. Themethod of claim 5, further comprising: receiving from the videodistribution network a program slot number and an identifier of theassigned modulator of the physical transmission path; and tuning to theprogram slot number and the assigned modulator of the physicaltransmission path to receive the video-on-demand data.
 7. The method ofclaim 5, further comprising extracting the modulator group identifierfrom program streams received from the video distribution network.